Disclosed herein is a process for preparing an aqueous ink jet printing ink containing nano-pigmented wax particles or dyed wax particles for improved release and gloss properties and which are suitable for use with a broad of color and printing media.
Ink jet printing technology often comprises jetting of inks onto a transfix belt or drum, followed by transferring of the ink onto a printing medium, such as paper, under pressure. This is often referred to as transfer or transfix ink jet printing. Ink jet printing technology also often involves jetting of inks directly onto printing media, such as direct to paper printing.
Inks formulated for transfer or direct ink jet printing technologies can comprise aqueous dispersions of dyes or pigments dispersed to have an “average” particle or drop size D50 of less than about 150 nanometers and which are stabilized using a dispersant, plus other ingredients including lubricant, solvents and binders. “Average” particle or drop size is typically represented as d50, or defined as the volume median particle size value at the 50th percentile of the particle size distribution, wherein 50% of the particles in the distribution are greater than the d50 particle size value, and the other 50% of the particles in the distribution are less than the d50 value. Average particle size can be measured by methods that use light scattering technology to infer particle size, such as Dynamic Light Scattering. The particle diameter refers to the length of an individual drop of the discontinuous layer as derived from images of the particles generated by Transmission Electron Microscopy or from Dynamic Light Scattering measurements.
Pigments are typically heavier than water and tend to agglomerate and settle unless they are stabilized by a dispersant.
Challenges associated with designing inks for transfix printing technology include achieving desired ink adhesion and release of the ink to the transfix belt or drum. To achieve the desired adhesion and release performances, a non-stick printing plate, i.e. a “blanket” can be used and an application of a layer of starch, i.e. “Skin”, and glycerol disposed to the transfix belt or drum before jetting inks.
Challenges associated with designing inks for direct-to-paper printing technology include the challenges related to printing onto different printing media, including coated paper, uncoated paper, or plastic, which can be hydrophilic or hydrophobic.
Inks are often jetted by print heads containing multiple nozzles. To prevent clogging of the nozzles, pigments require milling to achieve an acceptable particle size, typically to a D50 of less than about 130 nanometers and having a small standard deviation such as 1 nanometer. A long ink shelf life is desirable wherein the ink remains stable including having stable rheological properties over long periods of time. Pigments are denser than water. Inks manufactured with pigments rely on use of dispersants to prevent settling and agglomeration.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.